Master cylinder for brakes



R. A. GQEPFRICH MASTER CYLINDER FOR BRAKES Julie 2, 1942.

Original Filed March 10, 1938 assess: sras'rm. as non seamen A. stem-uh, South ma, Ina, acsiguor to Bendix Products Corporation, South Bend, 1nd, a corporation of Indiana Original application; March 10,1938, Serial No. 195,92! now Patent No. 2,262,848,; dam November 18, 1941. Divided and this application Decemlaer 21. 1940, Serial No. 371,074 r I" 4 (c1. si -54s) This invention relates to braking'systems of the hydraulic or fluid pressure type and more particularly to devices for producing fluid pressure to operate such braking systems. The instant application is a division or my copending application Serial No. 195,021, issued on November 18, 1941, as Patent No. 2,252,843.

In conventional fluid braking systems, the cylinder of the fluid pressure producing device is generally connected to the fluid reservoir by two ports known in. the art as the supply port and the compensating port. The latter (compensatins) port is usually located so that when the piston is in its maximum retracted position, the port is slightly ahead of a flexible cup seated on the piston head. As the piston travels on its compression stroke the resultant pressure at the head of the piston extends the flexible cup. This expansion of the cup retards the travel of the piston as the cup passes the compensating port. Sometimes the movement past the port even tears the cup. It is the aim of the invention of my copending application Serial No. 107,239, filed October 23, 1936, issued on June 27, 1939 as Patv ent No. 2,163,874, and alsothe object of the invention disclosed herein, to overcome this undesirable condition.

master cylinder showing the piston as in its retracted position.

. My novel master cylinder is shown incorporated with a general br system for a vehicle in Figure 1. As illustrated the said master cylln- 'der is indicated generally by the reierence numeral I05. 1.

An object, therefore, of this invention is-to provide a fluid pressure producing device wherein the cylinder is constructed in such a manner as to obviate any undesirable openinginto the fluid reservoir tending to be injurious to the piston cup. v

A further object 03 the invention is to provide a fluid pressure producing device having a novel piston permitting by-passing of fluid from the -r'eservoir through itself when the piston is in its retracted position. or during its retracting stroke.

A still further object of this invention is to provide a substantially shorter piston of this type than pistons heretofore proposed or used. Such a piston is simpler in construction, the cylinder bore required is relatively shorter, and the entire fluid pressure producing device consequently takes up less space in the vehicle with .the added feature of ease of construction of the entire unit at a substantially reduced cost or manufacture.

Other objects and desirable particular constructions and arrangement of parts will become apparent upon reference to the following detailed description of the illustrative embodiment shown in the accompanying drawing, in which:

.1 Figure 1 is a diagrammatic illustration of a fluid brake system embodying my invention; and

Figure'2 is a vertical section In'Figure 2 the master cylinder its is shown in section having a cylinder IlIiformedwith a discharge port H2, the cylinder being integrally formed with a fluid reservoir H6 whichhas a V vent plug HR for filling.

The cylinder no receives a reciprocablelpiston I20 suitably connected to a rod #22 having at one of its ends a ball lztflt'ted in arecess I26 at the rear of the piston and'a' clevis 82d at'its a fixed support, As pressure is applied to the foot pedal I02 the force is transmitted to the elevis are actuating the rod I22 causing the con sequent application. of the brakes in a manner to be hereinafter more fully described.

A fluid pressure delivery pipe Hi8 suitably connectedtothe discharge port N2 of the master cylinder lilo has-conduits connected respectively to fluid pressure actuated motors ti l" arranged in pairs; one pair for actuation of the brakes associated with the front wheels'of the vehicle,

and the other for actuation of the brakes associated with the rear wheels of the vehicle.

The brakes maybe of thestandard type each includingta fixed support or backing plate to, a

rotatable drum 52' associated with the backing plate, 'a pair of corresponding brake shoes 54 and 58 pivoted on the backingplate, and pressure actuated motors III mounted onthe backing plate 50 between each pair of shoes and operative to actuate the shoes into engagementwith the braking surface of the drum 52 against the resistance of a retractile spring 58 connecting the shoes.

A flexible boot I30 sleeved about the rod I22 and suitably fastened to the cylinder at one end and to the clevis I28 at the other end is provided to retain fluid therein and to be retractible with the rod I22.

The fluid reservoir I-I8- has a communication port I32 receiving a ported plug Ill extending into the cylinder 0. A

The piston I20 is constructed with a grooved cutaway portion about its inner periphery so as through my novel 55 to receive the rubber washer I" having lips whlch'upon the compression stroke .distend so as to a seal-tight closure !or the pan.

The piston further has a a; a 688 formed arly so as to receive the siideble grooved stem I400! the conical valve M2 ted in the angular conical m or s m- The stem its is provided with e lotudinal slot adapted to receive a retaining pin use.

The rear oi the piston H9 is provided with a "cut-away" portion so as to permit the val oi the piston without interference oi the exteng channeled plug IM, and to permit acumen-- tion oi the reservoir lit with the hollow boot 88d.

The rear ofthe piston is secured seamstressward displacement by the washer its split spring IEO.

tially the ter oi said end, said passage being 1 with respect to the axis of the piston one end through the iorward end oi the piston substantially on the axis of said The channeled plug I86 serves the double pur= pose oi acting as a communicationport and as a tripping member for the valve N2 when the piston is in its mum retracted tion to compensate for any fluid that may have'been lost throughout the system during the braking thereof In the operation of my device, as the foot pedal lever I02 is depressed. the force is transmitted through the .clevis I23 to the rod I82 which in turn starts the piston I20 on its compression stroke. The pressure created by the fluid at the head oi the piston I20 retains the valve Q42 in its seatprohibiting any book flow.

The resultant pressure of the compression stroke causes flow of fluid through the discharge port I I2 to the conduit I00 and into the motors II4 causing the mov against the force of t e rectractile spring 00.-

As the foot pedal I02 is released the rod I22 and piston I20 travel to their retracted position.

out of the shoes 04 and 08 The retaining pin I holds the valve I42 andavoids complete'displacement should vacuum be created on the upward stroke at the head of the piston. As the piston reaches its maximum retracted position, the plug or pin I24 at its rear contacts the stem I40 of the valve tripping it ofl its seat to permit inflow oi fluid from the reservoir should any have been lost in the system during the compression stroke.

While a single illustrative embodiment has been described in detail, it is not my intcnsion to limit the scope oi the invention to this parpiston and with the other-end terminating at the sw end of said piston at a point between the point or absent or said operating member and the adjacent wall or said cylinder; a i

valve for controlling said ing a stem pi8to,iaiid a stop upon said cylinder wall directly ag ng the stem ofsaid valve to unseat,

g n latter when the piston is in its retracted po-- t on.

2. In 7 a horizontal master cylinder, a fluid reservoir, 9. cylinder formed with said reservoir and adapted to communicate therewith, apisfon reciprocabie in said cylinder having a slotted portion permitting communication of fluid to the rear of said piston and having arr-angular pos sage-therethrough, a valve controlling said passage. means carried by the piston tov hold the valve against complete displacement on its return stroke. and a channeled member extending into the cylinder supplying fluid thereto and adapted to actuate said valve to open position when the piston is in its retracted position.

3. A fluid pressure producing device'comprising a cylinder, inder and having an angular 'by-pass therethrough. a valve controlling the by-pass. and a timid igiailying member extending' into the cylpass, and a supply tube extending into the cylinder adapted to actuate the valve to open position ticular embodiment, or otherwise than by the so on the return stroke of the piston.

terms of the appended claims.

I claim:

Rumor-PH a common.

a piston reciprocable in said cyl-' arranged to trip the valve toopen position when the piston is in its retracted position. 

